A.5.272 RDSHR: Read SMM Header Pointer Register
RDSHR r/m32 ; 0F 36 /0 [386,CYRIX,SMM]
RDSHR reads the contents of the SMM header pointer register and saves it
to the destination operand, which can be either a 32 bit memory location
or a 32 bit register.
See also WRSHR (section A.5.330).